NEUTRON-DIFFRACTION STUDIES OF NUCLEAR-ORDER IN SILVER AT PK TEMPERATURES

We have extended the range of neutron diffraction techniques down to p icokelvin temperatures in our experiments on spontaneous long range nu clear order of spin-1/2 nuclei in a single crystal of Ag-109 [1]. The observed antiferromagnetic phase had a simple 1-k structure and no fie ld induced phase transitions within the ordered state could be indenti fied. Neutron transmission measurements, based on spin dependent neutr on absorption were used to determine the nuclear susceptibility and en tropy.